Low-pressure casting apparatus

ABSTRACT

Low-pressure casting apparatus includes a holding furnace for molten metal which is sealed and supplied with gas under pressure. A riser pipe is immersed in the molten metal and communicates with the base plate of an ingot mold positioned on top of the holding furnace. Two opposed flat, upright members are positioned to the rear of the sidewalls of the holding furnace and a horizontal bridge member is mounted between the upright flat members. The bridge member has a forwardly opening U-shaped slot in which a tension element is horizontally slidably mounted. The tension element contains guide means for tension rods which are attached to the core cover plate, which is part of the ingot mold.

United States Patent [191 Diez et al.

[ 1 Sept. 11, 1973 LOW-PRESSURE CASTING APPARATUS [75] Inventors: Adolf Diez, Neckarsulm; Josef Heim,

Oedheim, both of Germany [73] Assignee: Karl Schmidt GmbH, Neckarsulm,

Germany 221 Filed: Jan. 19, 1972 21 Appl. No.: 218,887

[30] Foreign Application Priority Data Jan. 22, 1971 Germany P 21 02 884.2

[52] US. Cl 164/309, 164/339, 164/345 [51] Int. Cl 822d 17/06 [58] Field of Search 164/306, 309, 337,

[56] References Cited UNITED STATES PATENTS 3,017,675 l/l962 Young 164/339 X 3,450,190 6/1969 Mittermaier et al... 164/309 3,643,732

2/1972 Carlsen 164/137 X FOREIGN PATENTS OR APPLICATIONS 4,308 4/1963 Japan 164/306 Primary ExaminerRobert D. Baldwin Attorney-Burgess, Dinklage & Sprung [,57] ABSTRACT Low-pressure casting apparatus includes a holding furnace for molten metal which is sealed and supplied with gas under pressure. A riser pipe is immersed in the molten metal and communicates with. the base plate of an ingot mold positioned on top of the holding furnace. Two opposed flat, upright members are positioned to the rear of the sidewalls of the holding furnace and a horizontal bridge member is mounted between the upright flat members. The bridge member has a forwardly opening U-shaped slot in which a tension element is horizontally slidably mounted. The tension element contains guide means for tension rods which are attached to the core cover plate, which is part of the ingot mold.

13 Claims, 10 Drawing Figures PATENTEUSEPW975 3 "is? 850 saw 3 BF 7 Fig.)

LOW -PRESSURE CASTING APPARATUS BACKGROUND This invention relates to a low-pressure casting plant, which includes a holding furnace for molten metal which is adapted to be closed gas tight and supplied with gas under pressure, and a riser pipe immersed in the metal bath which is in communication with the base plate of an ingot mold having stationary or movable parts. The ingot mold is adapted to be closed at the top by a core cover plate having on its underside the core affixed thereto. The core cover plate is vertically movable by means of a plurality of hydraulically operated tension columns.

PRIOR ART Low-pressure casting has progressively increased in importance in recent years because it involves special processes which constitute a valuable contribution to the mechanization of ingot mold casting and is virtually a connecting link between ingot mold and die casting processes.

Low-pressure casting is based on the'concept of providing liquid molten metal in a holding furnace which is sealed air tight from the outside, and of supplying pressure gas into the furnace atmosphere to cause the liquid metal to rise into the ingot mold whichis located on top of the furnace. The ingot mold is thus filled with liquid metal from bottom to top and under comparatively low pressure. The application of pressure is continued during the solidification so taht the need for feeders is entirely eliminated. When the casting has solidified, a pressure relief is effected and liquid metal flows back from the riser pipe into the furnace. The separation between the casting and the liquid metal is effected by gravity at the top end of the riser pipe. A conical joint may be provided at the head of the riser pipe to effect the separation in this area.

The elimination of feeders is an important advantage afforded by low-pressure casting because it reduces the amount of metal in circulationIThus the cost of melting, holding and chipping are greatly reduced. Because the actual casting operation is initiated by the introduction of the pressure gas, the operator need not take and pour the metal by means of a ladle, as is conventional in other casting processes. As a result, one operator may operate a plurality of low-pressure casting plants at the same time. Another important advantage is that low-pressure casting makes possible the production of castings which have a high structural density and are free of shrinkage cavities.

In accordance with thepresent state of the art as disclosed in Giessereipraxis No. 15, (1970), pages 232-238; Giesserei 56, (1969), pages 83 to 90; Giesserei 49, (1962), pages 332-341; and wt-Z, ind. Fertig. 60, (1970) No. 3, pages 124-130, a low-pressure casting plant comprises a holding furnace which is gas tight and preferably electrically heated, and the positioning device for the ingot mold. Communication between the metal bath in the holding furnace and the ingot mold is established by a vertical riser pipe which is secured to the base plate of the ingot mold. The base plate is mounted on the cover of the holding furnace. Gas under a pressure of, e.g., 0.2-0.5 kilogram per square centimeter above atmospheric pressure is supplied to the holding furnace interior above the molten metal. When alloys are processed which are susceptible to oxidation, inert protective gases are suitably supplied to apply pressure.

The ingot mold includes a plurality of mold parts and is positioned on the base plate above the cover of the holding furnace. Depending on the casting to be made, the main parting plane of the ingot mold may be horizontal or vertical. The mold parts of the ingot mold may be stationary or may be movable by mechanical or hydraulic means. Where movable ingot mold parts are used, they are either locked in the casting position or are positively held together to resist the pressure which is applied by the liquid metal to the mold interior during the casting operation.

The ingot mold is adapted to be closed at its top by a core cover plate to the underside of which the core is fixed. The core cover plate is suspended from a plurality of, preferably four, hydraulically operated tension rods or shafts, which are secured at their top end to an abutment which is engaged by a hydraulic actuator. The opposite or lower end of the hydraulic actuator engages a head plate, by which the tension rods are guided in suitable guides. The head plate is screwconnected to the base plate by a plurality of so-called guide shafts.

Low-pressure casting plants, however, have been found to have the following disadvantages:

l. The head plate, which is screw-connected by four guide shafts to the mold base plate, and the abutment provided at the top end of the tension columns, are both disposed directly over the ingotmold so that ingot mold parts can only be installed and removed from the side in a difiicult and time-consuming operation requiring considerable effort;

2. The guide shafts are positioned such that the possibility of installing ingot mold parts differing in size is limited; a

3. The differentials in thermal expansion among the guide shafts connected to the base plate and the top plate secured thereto results in a canting causing the guides for the tension rods to bind;

4. Vertical adjustment of the tension rods when used in conjunction with ingot mold parts having different heights is complicated and time-consuming because the tension rods are vertically adjustable only by nuts;

5 The cores are secured to the core cover plate with screws so that considerable time is required in most cases to change the core;

6. The cover of the holding furnace may be removed only when a plurality of screws have been released, which is time-consuming;

7. The base plate of the ingot mold is secured to the cover of the holding furnace with screws so that replacement of the base plate takes a relatively long time. Another disadvantage resides in the fact that the tapped bores which are not utilized to secure the ingot mold are filled with molten metal as it escapes from the ingot mold;

8. Where the ingot mold comprises hydraulically movable parts, the hydraulic actuators which move these parts are secured to the guide shafts so that they must always be readjusted when different ingot mold parts are interchanged; and

9. A change of the riser pipe is fairly complicated because the entire positioning device must be removed from the holding furnace, e.g., by means of a fork lift truck, or must be swung rearwardlly through SUMMARY It is an object of the invention to provide a lowpressure casting plant wherein the foregoing disadvantages are eliminated making it possible to gain simple and easy access to the ingot mold parts and to the riser pipe and greatly increasing the versatility of low pressure casting.

According to the invention, low-pressure casting apparatus includes holding furnace means for molten metal adapted to be closed in known manner by cover means which carries the base plate means of the ingot mold means. Two opposite upright flat-section bars are positioned to the rear of the sidewall portions of the holding furnace means and horizontally positioned bridge means are mounted on the upright bars and are provided with laterally extending arms to the rear and front sides and a forwardly opening U-shaped aperture. Hydraulically operated tension means are horizontally slidably mounted in the U-shaped aperture and has guide means for tension rods attached to the core cover plate of the ingot mold means.

DESCRIPTION OF THE DRAWINGS The invention is represented by way of example in the drawings and will be explained more fully hereinafter.

FIG. 1 is a side elevation showing a low-pressure casting plant according to the invention.

FIG. 2 is a front elevation of the low-pressure casting plant of FIG. 1. v

FIG. 3 is a sectional view taken on line I-I in FIG. 2.

FIG. 4 is a longitudinal sectional view showing the upper portion of a flat-section bar and the bridge structure mounted thereon.

FIG. 5 is a transverse sectional view taken on line II-Il in FIG. 4.

FIG. 6 is a longitudinal sectional view showing the means for fixing the cover of the holding furnace.

FIG. 7 is a top plan view showing the means for fixing the cover of the holding furnace.

FIG. 8 is a longitudinal sectional view showing the damping elements for fixing the base plate of the ingot mold to the cover of the holding furnace.

FIG. 9 is a top plan view showing the means by which a hydraulic actuatoris secured to a cross-member of the ingot mold and by which one mold part of the ingot mold is secured to the tension rods.

FIG. 10 is a longitudinal sectional view. showing the rod-sleeve joint which is providedbetween the hydraulic actuator and the cross-member of the ingot mold and between the tension rods of the hydraulic actuator and the mold parts of the ingot mold.

Referring now to FIGS. 1 and 2, two diametrically opposite, vertically extending flat-section bars 2 are secured to the rear end of the side parts of the holding furnace l for a metal bath. A horizontally extending, box-like bridge structure 3 is connected to the top end of the flat-section bars 2 and has protruding arms at its rear and forward ends and is secured by clamping screws 4 to the flat-section bars 2. When the clamping screws 4 are loosened, the bridge structure 3 should not unintendedly be displaced downwardly along the flatsection bars 2. For this reason, each flat-section bar 2 is engaged at its rear end face by a clamping bar 5 (FIG. 4) which is connected to the bridge structure 3 by spring elements 6, which produce a predetermined pressure.

The bridge structure 3 has a U-shaped aperture 7 (FIG. 2) which is forwardly open and in which a tension element 10 is horizontally slidably mounted. The tension element 10 is connected to the hydraulic actuator 8 (FIG. 1) and guides the four tension columns 9. An abutment 12 is connected to the upper end of the tension columns 9 and to the hydraulic actuator 11 for the operation of the tension columns 9. The hydraulic actuator 11 is connected to its lower end to the tension element 10 (FIG. 2). The driver plate 13 is secured to the lower end of the four tension columns 9 and is formed on its underside with a T-shaped groove 14 (FIG. 2).

The core cover plate 16 has on its upper side a suitably shaped extension, which is inserted into the T- shaped groove 14. The core cover plate 16 is secured with wedges 15.

Referring to FIGS. 6 and 7, the holding furnace 1 is closed by the furnace cover 17, which is secured by six horizontally slidable fixing elements, each of which consists essentially of the bearing bracket 18, which is secured with screws 21 to the edge of the holding furnace, the hollow eccentric pin 19 which is mounted in the bearing bracket 18 and theclamping pins 20, which are disposed in the eccentric pin 19 and flattened on one side.

The base plate 22 of the ingot mold 23 is secured to the furnace cover 17 by clamping elements, which consist of clamping bars 24 formed with two end slots 25, each of which receives a pin 26, which is connected to a hook element 27 which engages the underside of the top edge of the cover 17 (FIGS. 1, 2, 3 and 8).

The mold parts of the ingot mold 23 are operated by hydraulic actuators 28. Each hydraulic actuator 28 is connected to the cross-member 32 of the ingot mold by a rod-sleeve joint, which comprises pins 30, which are mounted on the end face of the hydraulic actuator 28 and are each formed with an oblique bore 31 and exv tend into suitably shaped apertures of the crossmember 32 of the ingot mold. The connection is established by a key 29, which has been made by turningon a lathe and is inserted into a vertical bore in the crossmember 32 of the ingot mold and the oblique bore 31 of the pin 30. The same rod-sleeve jont is provided between the ingot mold parts 35 and the tension rods 34 of the hydraulic cylinder 28. (FIGS.1, 3, 9 and 10) DESCRIPTION Because the preferably box-shaped bridge structure is vertically slidably mounted on the upright opposed flat-section bars, the stroke length of the tension rods can be simply and quickly adjusted to the respective overall height of the ingot mold parts. The bridge structure is vertically adjusted by hydraulic actuator means which operate the tension rods. In addition, the complete separation of the tension means from the holding furnace means prevents canting of guide means in the tension means and thus eliminates binding of the tension rod in the guide means resulting from differentials in thermal expansion.

The positioning of the upright flat-section bars to the rear of the sidewalls of the housing for the holding furnace in combination with the U-shaped aperture in the bridge structure permits an incorporation of varying ingot mold parts, even if they are bulky, and a change of the riser pipe, in a vertical direction from above, e.g., with the aid of a conventional shop crane in a simple manner without considerable physical effort and without removing the positioning device from the holding furnace.

The tension means, which is horizontally slidably mounted in the U-shaped aperture of the bridge means, allows the casting to be dropped (depending on the core cover plate) directly onto a conveyor device which is disposed between the upright flat-section bars (e.g., chute 33 shown in FIG. 1) so that the operator need not remove the casting from the core cover plate and place it into a transport container. I According to an additional embodiment of the invention, the bridge structure is clamped to the flat-section bars by a plurality of clamping screws when the lowpressure casting plant is operating. If an interchange of the ingot mold parts requires a change of the stroke length of the tension rods, the clamping screws will be released. The bridge structure is then held in its adjusted position on the flat-section bars only by clamping bars which act on the rear end faces of the flatsection bars and are under a predetermined pressure exerted by springs which'connect the clamping bars to the bridge structure.

ln a further development of the invention, a coupling plate is provided at the lower end of the tension rods formed with a T-shaped aperture. The core cover plate has on its upperside a suitably shaped mateing extension which is inserted in the coupling plate aperture, the core cover plate being secured by wedges. This arrangement enables a quick replacement of the core cover plate required without special means.

A further improvement of the low-pressure casting plant is provided bythe invention in that a plurality of fastening elements for the cover of the holding furnace are secured to the edge of the opening of the holding furnace which enable a fast and simple opening of the cover and consist each of a bearing bracket, which is connected to the holding furnace, and an eccentric pin, which is journaled in the bearing bracket and has a bore which contains a horizontally slidable clamping bolt, which has a flat on one side on its forward portion and exerts a clamping action on the lower edge of the cover. 7 1

The base plate of the ingot mold can be replaced quickly and .without considerable effort because the base plate issecured to the ever of the holding furnace only with two clamping elements, which are easily releasable and can be fixed in a simple manner and bear on the longitudinal edges of the base plate. The clamping elements include a U-shaped clamping member, which is mounted on the base plate and in its end portions is formed with slots, and of screws, which extend through the slots and connect the U-shaped clamping member to hook elements. The hook elements engage the underside ofthe top rim of the cover of the holding furnace. This arragement enables a fixation of base plates in different sizes and shapes in any desired position.

According to a special feature of the invention, the ingot mold is frictionally and positively connected by rod-sleeve joints to the hydraulic actuators 2 in that two pins mounted on the end face of each hydraulic actuator and provided with oblique bores are fitted into corresponding apertures of the cross-members of the ingot mold and the connection is established by respective keys, which have been made by turning on the lathe and are inserted each into a vertical bore of the cross-member of the ingot mold and the oblique bore of the associated pin.

Similar means are used to connect the ingot mold parts to the tension rods of the hydraulic actuator.

What is claimed is:

1. ln low-pressure casting apparatus which comprises holding furnace means for a molten metal bath, said furnace means having cover means and being adapted to be closed gas tight and supplied with gas under pressure, ingot mold means positioned on top of said furnace means and including base plate means carrid by the cover means of said furnace means and core cover plate means having attached to the underside thereof core means, riser pipe means adapted to be immersed in said metal bath and communicating with the base plate means of the ingot mold means, and a plurality of upright tension rods adapted to vertically move the core cover plate means of said ingot mold, the improve ment which compises two opposite upright flat members positioned to the rear of the sidewalls of said furnace means and horizontal bridge means mounted between said upright flat members, said bridge means having a forwardly. opening U-shaped slot in which is horizontally slidablymounted tension means, said tension means having guide means for said tension rods, and said bridge means having means to horizontally slide said tension means.

2. Low-pressure casting apparatus of claim 1 wherein said ingot mold means includes movable mold means.

3. Low-pressure casting apparatus of claim 2 wherein said movable mold means are hydraulically activated.

4. Low-pressure casting apparatus of claim 1 wherein said tension rods are hydraulically activated.

a 5. Low-pressure casting apparatus of claim 1 wherein the tension means of said bridge means is hydraulically activated. 6. Low-pressure casting apparatus of claim 1 wherein said bridge means is vertically adjustably mounted between said upright flat members. i

7. Low-pressure casting apparatus of claim 6 wherein said bridge means is vertically adjustable by spring loaded clamping bar means adapted to engage and edge of each upright flat member.

8. Lowpressure casting apparatus of claim 1 which includes conveyer means mounted between said upright flat members and below said bridge means.

9. Low-pressure casting apparatus of claim 1 which includes grooved coupling means between said tension rods and the core cover plate means of said ingot mold means.

l0. Low-pressure casting apparatus of claim 1 wherein a plurality of fastening elements for the cover means of said holding'furnace means are secured to the edge of the opening of said furnace means, each including a bearing bracket and an eccentriepin journaled in the bearing bracket, said pin having a bore containing a horizontally slidable clamping bolt.

11. Low-pressure casting apparatus of claim 1 wherein said base plate means is secured to the cover means of said holding furnace means by clamping elements disposed adjacent to the longitudinal edges of said base plate means each including a U-shaped clamping member connected to hook elements which engage the underside of the upper rim of the cover means of said furnace.

wherein said ingot mold means includes movable mold parts connected to tension rods of hydraulic actuating means by rod-sleeve joints in that those ends of the tension rods which are adjacent the movable mold parts are provided with oblique bores and fitted into suitable apertures in the movable mold parts and the connection is established by respective keys each inserted into a vertical bore in said mold parts and into the oblique bore of the ends of the tension rods. 

1. In low-pressure casting apparatus which comprises holding furnace means for a molten metal bath, said furnace means having cover means and being adapted to be closed gas tight and supplied with gas under pressure, ingot mold means positioned on top of said furnace means and including base plate means carrid by the cover means of said furnace means and core cover plate means having attached to the underside thereof core means, riser pipe means adapted to be immersed in said metal bath and communicating with the base plate means of the ingot mold means, and a plurality of upright tension rods adapted to vertically move the core cover plate means of said ingot mold, the improvement which compises two opposite upright flat members positioned to the rear of the sidewalls of said furnace means and horizontal bridge means mounted between said upright flat members, said bridge means having a forwardly opening U-shaped slot in which is horizontally slidably mounted tension means, said tension means having guide means for said tension rods, and said bridge means having means to horizontally slide said tension means.
 2. Low-pressure casting apparatus of claim 1 wherein said ingot mold means includes movable mold means.
 3. Low-pressure casting apparatus of claim 2 wherein said movable mold means are hydraulically activated.
 4. Low-pressure casting apparatus of claim 1 wherein said tension rods are hydraulically activated.
 5. Low-pressure casting apparatus of claim 1 wherein the tension means of said bridge means is hydraulically activated.
 6. Low-pressure casting apparatus of claim 1 wherein said bridge means is vertically adjustably mounted between said upright flat members.
 7. Low-pressure casting apparatus of claim 6 wherein said bridGe means is vertically adjustable by spring loaded clamping bar means adapted to engage and edge of each upright flat member.
 8. Low-pressure casting apparatus of claim 1 which includes conveyer means mounted between said upright flat members and below said bridge means.
 9. Low-pressure casting apparatus of claim 1 which includes grooved coupling means between said tension rods and the core cover plate means of said ingot mold means.
 10. Low-pressure casting apparatus of claim 1 wherein a plurality of fastening elements for the cover means of said holding furnace means are secured to the edge of the opening of said furnace means, each including a bearing bracket and an eccentric pin journaled in the bearing bracket, said pin having a bore containing a horizontally slidable clamping bolt.
 11. Low-pressure casting apparatus of claim 1 wherein said base plate means is secured to the cover means of said holding furnace means by clamping elements disposed adjacent to the longitudinal edges of said base plate means each including a U-shaped clamping member connected to hook elements which engage the underside of the upper rim of the cover means of said furnace.
 12. Low-pressure casting apparatus of claim 1 wherein said ingot mold means includes movable mold parts connected by rod-sleeve joints to the hydraulic actuating means by pins provided on the end face of each hydraulic means and formed with an oblique bore fitted into corresponding apertures of the cross-member of the movable mold parts and the connection is established by respective keys each inserted into a vertical bore in said cross-member and into said oblique bore.
 13. Low-pressure casting apparatus of claim 1 wherein said ingot mold means includes movable mold parts connected to tension rods of hydraulic actuating means by rod-sleeve joints in that those ends of the tension rods which are adjacent the movable mold parts are provided with oblique bores and fitted into suitable apertures in the movable mold parts and the connection is established by respective keys each inserted into a vertical bore in said mold parts and into the oblique bore of the ends of the tension rods. 